Conventionally, an actuator for a pickup has been employed as a mechanism for recording data onto an optical recording medium and/or playing back the content thereof. Such the actuator for a pickup may have various types of constructions. In recent years, among various types of actuators for pickups, studies have been conducted on those capable of recording data onto an optical recording medium and/or playing back the content thereof at a higher-x speed.
For example, such the actuator for a pickup is equipped with a lens holder for supporting an objective lens, a magnet, and the like, a plurality of drive coils for driving the lens holder, a base, and four linear elastic members each connected at both ends thereof between the lens holder and the base. The lens holder is so supported as to be able to rock in a focusing direction and a tracking direction (e.g., Patent Document 1). This actuator for a pickup has been drawing attention especially for its advantages in weight saving and enhancement of bandwidth.
The aforementioned actuator for a pickup may have six or more linear elastic members (Patent Document 2).
In the actuator for a pickup constructed as described above, the four or six linear elastic members are designed such that the line segments linking their ends with each other constitute an oblong on a plane (i.e., a plane stretching perpendicularly to a longitudinal direction of the linear elastic members) including both a focusing direction and a tracking direction.
The lens holder rolls with respect to the base around a rotating center, namely, a center of a virtual circle circumscribed by those ends.
A center of the oblong substantially coincides with a center of mass of the lens holder and a drive center of the lens holder. In addition, the drive center of the lens holder coincides with a center of translational forces of the plurality of the linear elastic members.
[Patent Document 1]: JP 2001-229555 A (FIGS. 15 and 16)
[Patent Document 2]: JP 08-273179 A (paragraph [0031])